The present specification relates generally to liquid natural gas production and, in particular, to a method for natural gas liquefaction and filtration of solidified carbon dioxide.
Generally, natural gas refers to a methane-rich gas mixture that can include carbon dioxide, nitrogen, hydrogen sulfide, other hydrocarbons, and moisture in various proportions. In at least some known applications, natural gas is used as an alternative to other known fuels such as gasoline and diesel. To be used as an alternative fuel, or to facilitate storage and/or transport, natural gas is typically processed to convert the natural gas into liquefied natural gas (LNG). Typically liquefying natural gas includes cooling the natural gas to about the liquefaction temperature of methane, which is about −161° C. under atmospheric pressure. However, since some commonly found constituents of natural gas (e.g., moisture and carbon dioxide) have higher freezing points than methane, solidification of the constituents may occur when cooled to the liquefaction temperature of methane, thereby forming a LNG-rich slurry. The LNG-rich slurry is generally unsuitable for use as alternative fuel. Impurities freezing in a heat exchanger during natural gas liquefaction also can cause operational problems during LNG production.
Conventional methods of forming purified LNG typically includes removing CO2 in the raw natural gas before cooling it to the liquefaction temperature of methane. However, known removal systems are costly to implement and generally have a relatively large ecological and/or physical footprint. Other known methods of forming purified LNG include removing the solidified CO2 from LNG via gravity separation and/or cyclone separation. However, while such removal methods are generally effective at removing relatively large solidified CO2 particles from the LNG-rich slurry, they are less effective at removing smaller particles.
Therefore, there is need for an improved method for natural gas liquefaction and filtration of solid carbon dioxide particles.